The disclosure presented here involves an effect device that can easily connect with other effect devices in parallel. A preferred embodiment of this device is equipped with a number of components including an effect add means that adds effects, a mixing means that mixes the musical signals, a mode switching means that configures the operation from parallel mode to serial mode, and a phase reversal means that reverses the phase of the musical sound signals. Various combinations using the above means are possible and are presented in this disclosure. The output terminal outputs the musical sound signals that were selected, mixed, and or treated by the enabled features of the underlying embodiments.